Faisal Sharif

Superparamagnetic iron oxide nanoparticle targeting of MSCs in vascular injury

Vascular occlusion can result in fatal myocardial infarction, stroke or loss of limb in peripheral arterial disease. Interventional balloon angioplasty is a common first line procedure for vascular disease treatment, but long term success is limited by restenosis and neointimal hyperplasia. Cellular therapies have been proposed to mitigate these issues; however efficacy is low, in part due to poor cell retention. We show that magnetic targeting of mesenchymal stem cells gives rise to a 6-fold increase in cell retention following balloon angioplasty in a rabbit model using a clinically applicable permanent magnet. Cells labelled with superparamagnetic iron oxide nanoparticles exhibit no negative effects on cell viability, differentiation or secretion patterns. The increase in stem cell retention leads to a reduction in restenosis three weeks after cell delivery.

Gene-eluting Stents: Adenovirus-mediated Delivery of eNOS to the Blood Vessel Wall Accelerates Re-endothelialization and Inhibits Restenosis

Drug-eluting stents for coronary artery disease results in inhibition of smooth muscle cell (SMC) and endothelial cells which may increase the risk of stent thrombosis. In this study, we attempted to enhance re-endothelialization of deployed stents while simultaneously inhibiting intimal hyperplasia by overexpression of endothelial nitric oxide synthase (eNOS) delivery in the vasculature using an adenovirus gene-eluting stent. Re-endothelialization was significantly greater in vessels obtained from normocholesterolemic animals at day 14 (85.34% +/- 7.38 versus 62.66% +/- 10.49; P < 0.05) and day 28 (91.1% +/- 10 versus 63.1% +/- 22; P < 0.05) and hypercholesterolemic animals (96.97% +/- 3.2 versus 28.33% +/- 38.76; P < 0.05) at day 28 with AdeNOS-eluting stents. At day 28, there was a significant increase in the lumen size [AdeNOS 2.73 mm(2) +/- 1.18, AdbetaGal 0.98 mm(2) +/- 0.98, phosphorylcholine (PC) 1.87 mm(2) +/- 1.18; P < 0.05], and a significant reduction in neointimal formation (AdeNOS 2.32 mm(2) +/- 1.13, AdbetaGal 3.73 mm(2) +/- 0.95, PC 3.2 mm(2) +/- 0.94; P < 0.05), and percent restenosis (AdeNOS 45.23 +/- 20.81, AdbetaGal 79.6 +/- 20.31, PC 70.16 +/- 22.2; P < 0.05) in AdeNOS-stented vessels in comparison with controls from hypercholesterolemic animals, assessed by morphometry and quantitative coronary angiography (AdeNOS 15.95% +/- 7.63, AdbetaGal 56.9% +/- 38.6, PC 58 +/- 34.6; P < 0.05). Stent-based delivery of AdeNOS results in enhanced endothelial regeneration and reduction in neointimal formation as compared with controls. This seems to be a promising treatment strategy for preventing in-stent restenosis (ISR) while simultaneously reducing the risk of stent thrombosis.

Effect of gene delivery of NOS isoforms on intimal hyperplasia and endothelial regeneration after balloon injury.

Endothelial cell loss is a critical event in the pathological repair of the injured blood vessel. Impaired endothelial function results in reduced production of key vascular mediators such as nitric oxide (NO) within the vessel wall leading to enhanced smooth muscle cell proliferation and migration and ultimately intimal hyperplasia. The aim of the present study was to directly compare the effects of adenoviral-mediated gene delivery of two nitric oxide synthase (NOS) isoforms, eNOS and iNOS on endothelial regeneration and intimal hyperplasia following endothelial injury in the rabbit carotid artery. The right carotid arteries of male New Zealand white rabbits were denuded by passing a 3French Fogarty balloon catheter along the artery three times. In all, 1 × 109 PFU of adenoviral(Ad)eNOS, AdiNOS or Adβ-galactosidase (Adβ-Gal) was then delivered intraluminally and allowed to dwell for 20 min. Transgene expression was sought after 3 days by immunohistochemistry and at 7 days by quantitative reverse transcriptase PCR. The effect on intimal hyperplasia was sought using histological staining after 14 days. Evans blue staining was used to determine the effect on endothelial regeneration. eNOS and iNOS expression was detected in transduced arteries. Neointima/media ratios were significantly reduced in eNOS (0.07±0.044) and iNOS (0.087±0.086) transduced arteries compared with Adβ-Gal (0.332±0.14) transduced arteries (n=7). In addition, AdeNOS treatment (4.21±3.12% de-endothelialized area) enhanced endothelial regeneration compared to Adβ-Gal treatment (10.05±4.98), while treatment with AdiNOS (25.17±11.92) inhibited endothelial regeneration in the injured rabbit carotid artery (n=7–8). These results highlight the potential of NOS gene therapy, in particular, eNOS gene therapy as a potential therapeutic strategy for the prevention of restenosis after vascular injury.

Current status of vulnerable plaque detection

Critical coronary stenoses have been shown to contribute to only a minority of acute coronary syndromes (ACS) and sudden cardiac death. Autopsy studies have identified a subgroup of high‐risk patients with disrupted vulnerable plaque and modest stenosis. Consequently, a clinical need exists to develop methods to identify these plaques prospectively before disruption and clinical expression of disease. Recent advances in invasive and noninvasive imaging techniques have shown the potential to identify these high‐risk plaques. The anatomical characteristics of the vulnerable plaque such as thin cap fibroatheroma and lipid pool can be identified with angioscopy, high frequency intravascular ultrasound, intravascular MRI, and optical coherence tomography. Efforts have also been made to recognize active inflammation in high‐risk plaques using intravascular thermography. Plaque chemical composition by measuring electromagnetic radiation using spectroscopy is also an emerging technology to detect vulnerable plaques. Noninvasive imaging with MRI, CT, and PET also holds the potential to differentiate between low and high‐risk plaques. However, at present none of these imaging modalities are able to detect vulnerable plaque neither has been shown to definitively predict outcome. Nevertheless in contrast, there has been a parallel development in the physiological assessment of advanced atherosclerotic coronary artery disease. Thus recent trials using fractional flow reserve in patients with modest non flow‐limiting stenoses have shown that deferral of PCI with optimal medical therapy in these patients is superior to coronary intervention. Further trials are needed to provide more information regarding the natural history of high‐risk but non flow‐limiting plaque to establish patient‐specific targeted therapy and to refine plaque stabilizing strategies in the future.

Adenoviral-Mediated Gene Transfer of Nitric Oxide Synthase Isoforms and Vascular Cell Proliferation

Objective: Many vascular diseases are associated with reduced nitric oxide (NO) bioavailability. Nitric oxide synthase (NOS) gene therapy to the vasculature is a possible treatment for vascular disease as a means of increasing NO bioavailability, and this may be achieved using any of the NOS isoforms. The aim of our study was to compare the effects of adenoviral-mediated overexpression of the most commonly used NOS isoforms eNOS and iNOS on vascular cell proliferation. Methods: Human coronary artery smooth muscle cells (HCSMCs) and human umbilical vein endothelial cells (HUVECs) were transduced with adenoviral vectors encoding eNOS or iNOS at a multiplicity of infection of 100. Control cells were exposed to AdNull (empty vector) or diluent alone. Transgene expression was sought by Western blotting. The Greiss assay was used to measure nitrite levels. Cell proliferation was assessed by cell counting on days 0, 3 and 6. Apoptosis was sought using FACS analysis. Angiogenesis was measured using a commercially available in vitro kit. Results: Expression of both isoforms was detected in transduced cells by Western blot at all three time points. NOS transduction resulted in increased nitrite levels with higher levels seen in iNOS- compared to eNOS-transduced cells. Cell proliferation was diminished in AdeNOS- and AdiNOS-transduced cells compared with non-transduced cells on days 3 and 6 in both HCSMCs and HUVECs. Apoptosis was not detected in either cell line with either of the isoforms at any timepoint studied. Both eNOS and iNOS gene transfer caused a reduction in angiogenesis. Conclusions: NOS gene transfer to both endothelial and vascular smooth muscle cells is antiproliferative and antiangiogenic. The biological effect is identical with both isoforms and there is no evidence to support a differential effect on endothelial and vascular smooth muscle cell biology.

Proceedings from the 2nd European Clinical Consensus Conference for device-based therapies for hypertension: state of the art and considerations for the future

Abstract

Long-term follow-up of percutaneous coronary intervention of unprotected left main lesions with drug eluting stents: predictors of clinical outcome.

AIMS To evaluate the long-term follow-up of drug-eluting stents (DES) in the treatment of unprotected left main coronary artery (ULMCA). METHODS AND RESULTS One hundred and forty-eight patients (mean age 71 +/- 10 years) with ULMCA stenoses underwent percutaneous coronary intervention (PCI) with DES. Mean ejection fraction (EF) was 63 +/- 13% and distal ULMCA was involved in 63.5% of cases. In-hospital outcome showed one intra-procedural death, no stent thrombosis and 2% non Q-wave myocardial infarction (MI). Clinical follow-up was available in all patients (874 +/- 382 days): 10.1% of them had died, 8.8% had target lesion revascularisation (TLR) and 4.1% experienced MI. Major adverse cardiac events (MACE) occurred in 20.3%. Mortality predictors were EF < or = 55% (OR 3.6, 95%-C.I. 1.3-10.1, p = 0.016) and EuroSCORE > or = 6 (OR 3.9, 95%-CI 1.1-14.1, p = 0.037). TLR predictors were distal lesion (OR 8.5, 95%-CI 1.1-15, p = 0.041) and age < 64 years (OR 3.1, 95%-CI 1-9, p = 0.042). MACE predictor was EF < or = 55% (OR 2.4, 95%-CI 1.1-5.2, p = 0.027). CONCLUSIONS ULMCA stenting with DES is safe, with favourable in-hospital outcome. Long-term results are acceptable with a mortality rate of 10%, a TLR rate of 9%, and a MACE rate of 20%. Low EF and high EuroSCORE predict mortality, while younger age and distal lesions predict TLR. Low EF also predicts MACE.

Long-term clinical outcome in patients with small vessel disease treated with drug-eluting versus bare-metal stenting

BACKGROUND DES is superior to BMS in reducing restenosis and repeat revascularization. Available data are less convincing in small vessel disease. Aim of our study is to assess long-term clinical outcome of drug-eluting stents (DES) vs. bare-metal stents (BMS) in small coronary vessel disease. METHODS Procedural and long-term clinical outcomes were assessed in consecutive patients (pts) treated with stenting of native small coronary arteries (reference vessel diameter and implanted stent < 3mm). RESULTS Pts enrolled were 645: DES group (n = 277) presented more frequently diabetes (173 [62%] vs. 32 [9%], P < .0001), higher body mass index (27 ± 5 vs. 26 ± 4, P = .01) and with previous PCI (115 [42%] vs. 118 [32%], P = .01) as compared to BMS group (n=368). DES group presented more frequently with unstable angina (46 [17%] vs. 38 [10%], P = .02); BMS group presented more frequently with myocardial infarction (103 [28] vs. 43 [15], P = .0002). Reference vessel (2.27 ± 0.36 vs. 2.24 ± 0.36, P = .29), minimal lumen (0.81 ± 0.32 vs. 0.80 ± 0.31, P = .84) and stent diameter (2.59 ± 0.17 vs. 2.60 ± 0.15, P = .69) did not differ between the 2 groups. Lesion length was significantly higher in DES group (15.85 ± 6.81 vs. 13.66 ± 7.18, P = .01). At a median clinical follow-up of 3.0 years (IQR range 2.2-4.6), pts with DES showed significantly lower major adverse cardiac events (MACE, HR 0.51, 95%CI 0.33-0.78) and target vessel revascularization (TVR, HR 0.44, 95%CI 0.25-0.78). No differences were observed between the two groups as to death, myocardial infarction and stent thrombosis. CONCLUSIONS In small vessel disease, DES was more frequently implanted in pts at higher risk of restenosis, though it demonstrated to be more effective than BMS in reducing MACE and TVR at long-term follow-up.

Coronary Stent Materials and Coatings: A Technology and Performance Update

This paper reviews the current state of the art for coronary stent materials and surface coatings, with an emphasis on new technologies that followed on from first-generation bare metal and drug-eluting stents. These developments have been driven mainly by the need to improve long term outcomes, including late stent thrombosis. Biodegradable drug-eluting coatings aim to address the long term effects of residual durable polymer after drug elution; the SYNERGY, BioMatrix, and Nobori stents are all promising devices in this category, with minimal polymer through the use of abluminal coatings. Textured stent surfaces have been used to attached drug directly, without polymer; the Yukon Choice and BioFreedom stents have some promising data in this category, while a hydroxyapatite textured surface has had less success. The use of drug-filled reservoirs looked promising initially but the NEVO device has experienced both technical and commercial set-backs. However this approach may eventually make it to market if trials with the Drug-Filled Stent prove to be successful. Non-pharmacological coatings such as silicon carbide, carbon, and titanium–nitride-oxide are also proving to have potential to provide better performance than BMS, without some of the longer term issues associated with DES. In terms of biological coatings, the Genous stent which promotes attachment of endothelial progenitor cells has made good progress while gene-eluting stents still have some practical challenges to overcome. Perhaps the most advancement has been in the field of biodegradable stents. The BVS PLLA device is now seeing increasing clinical use in many complex indications while magnesium stents continue to make steady advancements.

Evaluation of hemodynamically severe coronary stenosis as determined by fractional flow reserve with frequency domain optical coherence tomography measured anatomical parameters

OBJECTIVES The main objective of this study is to determine the correlation between fractional flow reserve (FFR)- and frequency domain optical coherence tomography (FD-OCT)-measured lumen parameters, and to determine the diagnostic competence of FD-OCT concerning the identification of severe coronary stenosis. METHODS A total of 41 coronary stenoses in 30 patients were assessed consecutively by quantitative coronary angiography (QCA), FFR, and FD-OCT. Stenoses were labeled severe if FFR ≤ 0.80. The minimal lumen area (MLA), minimal lumen diameter (MLD), and percent lumen area stenosis (%AS) were measured using FD-OCT. RESULTS FFR was ≤ 0.80 in 10 stenoses (24.4%). A poor but significant correlation between FFR and FD-OCT-measured MLA (r(2) = 0.4, p < 0.001), MLD (r(2) = 0.28, p < 0.001), and %AS (r(2) = 0.13, p = 0.02) was found. In the overall group, the diagnostic efficiency of MLA and MLD in identifying significant stenosis was moderate. The area under the curve (AUC) was 0.80 [95% confidence interval (CI): 0.64-0.91] for MLA and 0.76 (95% CI: 0.60-0.88) for MLD. The best cut-off values of FD-OCT-measured lumen parameters to identify stenosis with FFR ≤ 0.80 were 1.62 mm(2) [specificity 97%, sensitivity 70%, positive predictive value (PPV) 89% and negative predictive value (NPV) 91%] for MLA and 1.23 mm (specificity 87%, sensitivity 70%, PPV 64% and NPV 90%) for MLD. The diagnostic efficiency of MLA in identifying significant stenosis in vessels having reference diameter < 3 mm was high. The AUC was 0.96 (95% CI: 0.83-1.0). CONCLUSIONS The FFR values and FD-OCT anatomical parameters MLA, MLD were found to be significantly correlated. In the overall group, the FD-OCT-measured MLA and MLD have shown moderate diagnostic efficiency in the functional evaluation of significant stenosis. FD-OCT-measured MLA has high diagnostic efficiency in identifying severe coronary stenosis in vessels having reference diameter < 3 mm.